The present invention relates to a flexible seal assembly for sealing between abutting surfaces in a turbine and particularly relates to a flexible seal assembly disposed between a gas turbine nozzle retaining ring and a shroud for minimizing or precluding leakage flow of compressor discharge air into the hot gas path. The present invention also relates to a method of assembling the flexible seal assembly.
In turbines, it is necessary to seal between certain components. For example, in a gas turbine, a nozzle retaining ring and shrouds have abutting opposed surfaces interposed between compressor discharge air on one side of the surfaces and the hot gas path on the opposite side. Typically a seal plate is disposed between the nozzle retaining ring and the shrouds at their interfaces. The nozzle retaining ring, however, is subjected to temperature gradients on the order of 200–300° F. as well as very large mechanical loadings. Moreover, the nozzle retaining ring, seal plate and shrouds are fabricated of different materials with different coefficients of thermal expansion. During turbine start up and shutdown cycles, the interfaced parts are mismatched thermally. Also, because the seal plate is bolted to the retaining ring wall, the seal plate and retaining ring distort simultaneously. These distortions caused by combined thermal and mechanical loadings in cyclic operations cause the nozzle retaining ring to deform with the result that the seal plate is not adequate to seal leakage gaps which develop between the nozzle retaining ring and the shrouds. Accordingly, there is a need for an effective seal between the nozzle retaining ring and shrouds which can accommodate thermal and mechanical distortions of the nozzle retaining ring during cyclic operations to minimize or preclude leakage flow through gaps at the interface of the ring and the shrouds.